Just a year ago, the colors were bright under the waves. Now the Maldivian reef is dead, the coral killed by the pressure of rising ocean temperatures. What is left is gray, a scene repeated in reefs around the world. Coral reefs are areas underwater where small creatures live. The coral is hard material formed on the bottom of the sea by the skeletons of those creatures. Usually brightly colored fishes swim among the coral. The world has lost about half its coral reefs in the last 30 years. Scientists are working to prevent their destruction. The health of the planet depends on it. This isn't something that's going to happen 100 years from now. We're losing them right now, said marine biologist Julia Baum of Canada's University of Victoria. We're losing them really quickly, much more quickly than I think any of us ever could have imagined. Scientists say global warming is causing the rising ocean temperatures.